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51.
We propose a general stochastic model for the UT1/LOD system and derive the corresponding Kalman filter model. This stochastic model consists of an arbitrary sum of continous time autoregressive moving average (ARMA) processes, each chosen to characterize a different frequency band. The transition matrix which corresponds to the overall system and the time-dependent process noise covariance matrix are derived.Based on the general formulation, several models for UT1 were derived from spectral analysis of the Space 92 UT1 series (Gross,1993). Using Space 92 as the reference series, the candidate models were compared based on their ability to predict UT1 and LOD up to 30 days in the absence of data. These candidate models were compared with the JPL operational Kalman Earth Orientation Filter (KEOF) which assumes a random walk model for LOD (Morabito et al.,1987). The results of the comparison revealed that autoregressive modeling the 40–50 day oscillation in the LOD reduces the LOD prediction error by 10prediction. 相似文献
52.
Sorption of dissolved Fe2+ on bentonite was studied using a batch technique. The distribution coefficient, Kd , was evaluated for a bentonite-iron system as a function of contact time, pH, sorbent and sorbate concentrations, and temperature. Sorption results were interpreted in terms of Freundlich's and Langmuir's equations. Thermodynamic parameters for the sorption system were determined at three temperatures: 298°, 308°, and 318°K. The values of ΔH°(-4.0 kjmol−1 ) and ΔG°(-2.46 Kjmol−1 ) at 298°K (25°C) suggest that sorption of iron on bentonite is an exothermic and a spontaneous process. The ΔG° value became less negative at higher temperatures and, therefore, less iron was sorbed at higher temperatures. The desorption studies with 0.01 M CaCl2 and deionized water at iron loading on bentonite showed that more than 90 wt% of the iron is irreversibly sorbed, probably due to the fixation of the iron by isomorphous replacement in the crystal lattice of the sorbent. 相似文献
53.
Abdessamad Najine Mohammed Jaffal Kamal El Khammari Tahar Aïfa Driss Khattach Mahjoub Himi Albert Casas Said Badrane Hicham Aqil 《Comptes Rendus Geoscience》2006,338(10):676-682
This study is based on the analysis and the interpretation of the gravity data of the Tadla basin. Its purpose is to increase the knowledge of this basin structure. A residual anomaly map was first calculated from the Bouguer anomaly data witch are strongly affected by a regional gradient. The computed map provides information on the ground density variation but it does not bring enough of new elements. Data filtering allows us to emphasize the structures affecting the basin. We chose the horizontal gradient coupled to the upward continuation techniques that permit to highlight news structures and to give information on their dip. The elaborated structural map of the study area constitutes a useful document for rationalizing the future groundwater exploration in the Tadla basin. To cite this article: A. Najine et al., C. R. Geoscience 338 (2006). 相似文献
54.
Almadani Sattam Abdelrahman Kamal Ibrahim Elkhedr Al-Bassam Abdulaziz Al-Shmrani Awad 《Arabian Journal of Geosciences》2015,8(4):2347-2357
Arabian Journal of Geosciences - Microtremor horizontal-to-vertical spectral ratio (HVSR) method has been conducted at 33 sites in Ahud Rufeidah urban expansion zone in order to assess the... 相似文献
55.
56.
Experiments on integral length scale control in atmospheric boundary layer wind tunnel 总被引:2,自引:1,他引:1
Accurate predictions of turbulent characteristics in the atmospheric boundary layer (ABL) depends on understanding the effects of surface roughness on the spatial distribution of velocity, turbulence intensity, and turbulence length scales. Simulation of the ABL characteristics have been performed in a short test section length wind tunnel to determine the appropriate length scale factor for modeling, which ensures correct aeroelastic behavior of structural models for non-aerodynamic applications. The ABL characteristics have been simulated by using various configurations of passive devices such as vortex generators, air barriers, and slot in the test section floor which was extended into the contraction cone. Mean velocity and velocity fluctuations have been measured using a hot-wire anemometry system. Mean velocity, turbulence intensity, turbulence scale, and power spectral density of velocity fluctuations have been obtained from the experiments for various configuration of the passive devices. It is shown that the integral length scale factor can be controlled using various combinations of the passive devices. 相似文献
57.
Post-collisional alkaline magmatism (∼610–580 Ma) is widely distributed in the northern part of the Neoproterozoic Arabian-Nubian Shield (ANS), i.e. the northern part of the Egyptian Eastern Desert and Sinai. Alkaline rocks of G. Tarbush constitute the western limb of the Katharina ring complex (∼593 ± 16 Ma) in southern Sinai. This suite commenced with the extrusion of peralkaline volcanics and quartz syenite subvolcanics intruded by syenogranite and alkali feldspar granite. The mineralogy and geochemistry of these rocks indicate an alkaline/peralkaline within-plate affinity. Quartz syenite is relatively enriched in TiO2, Fe2O3, MgO, CaO, Sr, Ba and depleted in SiO2, Nb, Y, and Rb. The G. Tarbush alkaline suite most likely evolved via fractionation of mainly feldspar and minor mafic phases (hornblende, aegirine) from a common quartz syenite parental magma, which formed via partial melting of middle crustal rocks of ANS juvenile crust. Mantle melts could have provided the heat required for the middle crustal melting. The upper mantle melting was likely promoted by erosional decompression subsequent to lithospheric delamination and crustal uplift during the late-collisional stage of the ANS. Such an explanation could explain the absence or scarce occurrence of mafic and intermediate lithologies in the abundant late- to post-collisional calc-alkaline and alkaline suites in the northern ANS. Moreover, erosion related to crustal uplift during the late-collision stage could account for the lack or infrequent occurrence of older lithologies, i.e. island arc metavolcanics and marginal basin ophiolites, from the northern part of the ANS. 相似文献
58.
A. Deif Azza Abed Kamal Abdel-Rahman Enayat Abdel Moneim 《Arabian Journal of Geosciences》2011,4(5-6):855-861
Recent and paleo seismicity indicate that moderate seismic activity is relatively large for Aswan area. This is a warning on the possibility of occurrence of earthquakes in the future too. No strong motion records are available in Aswan area for engineers to rely upon. Consequently, the seismological modeling is an alternative approach till sufficient instrumental records around Aswan become available. In the present study, we have developed new ground motion attenuation relationship for events spanning 4.0?≤? M w?≤?7.0 and distance to the surface projection of the fault up to 100 km for Aswan based on a statistically simulated seismological model. We generated suites of ground motion time histories using stochastic technique. The ground motion attenuation relation describes the dependence of the strength of the ground motions on the earthquake magnitude and distance from the earthquake. The proposed equation for peak ground acceleration (PGA) for the bed rock is in the form of: $ {\mathbf{log}}{\text{ }}\left( {{\mathbf{PGA}}/{\mathbf{gal}}} \right){\text{ }} = {\mathbf{1}}.{\mathbf{24}} + {\mathbf{0}}.{\mathbf{358}}{M_{\mathbf{w}}} - {\text{ }}{\mathbf{log}}\left( {\mathbf{R}} \right){\text{ }}-{\text{ }}{\mathbf{0}}.{\mathbf{008}}{\text{ }}{\mathbf{R}}{\text{ }} + {\text{ }}{\mathbf{0}}.{\mathbf{22}}{\text{ }}{\mathbf{P}} $ . Where PGA is the peak ground acceleration in gal (cm/s2); Mw, its moment magnitude; R is the closest distance between the rupture projection and the site of interest; and the factor P is a dummy variable. It is observed that attenuation of strong motion in Aswan is correlated with those used before in Egypt. 相似文献
59.
Ras Banas Peninsula is a large triangular tract of land jutting out into the Red Sea. It extends about 40 km eastward out of the general trend of the Red Sea coast of Egypt, covering an area of about 600 km2. Three sandy spits are jutting out from the main body of the peninsula into the Red Sea, possibly representing relics of structural trends, two of which are located at the western part and the third one is extending from the eastern edge forming a further seaward extension of the main body. A series of isometric and contour maps of the whole area under investigation are provided in digitized visual form of geomorphologic features, landforms and slope configuration. According to difference in relief, the study area can be subdivided into three topographic divisions, namely coastal plain (<50 m), medium-height land (50–150 m) and hinterland (>150 m). Drainage and lineament maps of the drainage networks were prepared from the topographic map and satellite images of the area. The prepared lineament map shows four main trends that control the configuration of the drainage system in the study area. These trends are Aqaba trend (NE–SW to NNE–SSW), Red Sea trend (NW–SE to NNW–SSE), Nubian trend (N–S), and Tethyan trend (E–W). It is clear that the structural trends, lithology and general slope are the main controls of developing parallel and dendritic drainage patterns in the area. Both geomorphology and drainage system configuration have great influences on the land use and natural hazards affecting the peninsula especially torrential floods and sea level fluctuations. 相似文献
60.
Mina Kaboudarahangi Osman Mohd Tahir Mustafa Kamal M.S. 《The Australian geographer》2013,44(2):197-213
Malaysia has a complex multiracial population, predominantly defined by three major ethnic groups: Malay, Chinese and Indian races, with diverse cultural backgrounds. Despite this, the country has a vision to be the most beautiful garden nation, and its National Landscape Policy (NLP) puts emphasis on creating a unique landscape and garden identity. Because of ethnic and cultural differences, there are differences between preferences for developing a garden identity for Malaysia. Hence, this study focused on the visual quality of gardens. Representative images of four well-established gardens of the world including Persian-Islamic, English, Japanese and Chinese gardens were presented to the study's respondents through preference photo surveys. Respondents from the three major ethnic groups in Malaysia were asked to rate their preferred garden types, elements and scenes that they would like to see in Malaysian gardens. The results pinpointed expectations of the visual quality of gardens. These highlighted some similarities and differences between the three major ethnic groups in their preferences for the scenes and elements that they sought in gardens. Diverse factors must be considered when creating Malaysian gardens that will be accepted by Malaysians of different ethnic groups. Garden development reveals preferences attached to visual qualities and emphasises cultural differences between garden users. 相似文献